Brake mechanism

ABSTRACT

A brake mechanism is mounted on a vehicle and includes a housing having a slot for receiving a rotatable disc to be braked. The upper portion of the housing includes a chamber for receiving pressurized fluid from a source. A spring actuated piston is slidably and sealingly disposed within the chamber. A removable spring assembly is positioned forwardly of the actuating piston and exerts a preselected spring force thereon. When the fluid pressure acting against the piston is less than the spring force applied to the piston, the piston moves axially in the chamber and a rod portion thereof contacts a lever that is pivotally mounted to the housing. The lever pivots on the housing to axially displace a brake applicator piston that is movably positioned in the housing adjacent to the rotatable disc. A plurality of braking pads are secured to the end portion of the applicator piston and additional braking pads are secured to the brake housing opposite the disc. Displacement of the applicator piston moves the braking pads into braking engagement with the disc to overcome rotation of the disc and stop the vehicle. In the event fluid pressure in the chamber diminishes, the spring assembly is automatically actuated to exert a parking brake force and move the braking pads into braking engagement with the disc. The spring assembly may be locked in a compressed state for efficient removal from the housing for maintenance or replacement and includes a device for visually indicating the wear condition of the braking pads.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 641,941 filedon Dec. 18, 1975, entitled "Improved Brake Mechanism" which in turn is acontinuation-in-part of application Ser. No. 508,741 filed on Sept. 24,1974, entitled "Brake Mechanism," and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a brake mechanism and more particularly to abrake mechanism associated with a hydraulic circuit and having aremovable spring assembly operable to actuate a service brake and applya preselected braking force to a rotating disc to automatically actuatea park brake in the event of hydraulic failure.

2. Description of the Prior Art

Conventional fluid actuated braking systems which are associated with ahydraulic circuit and are operable to brake the vehicle by applying abraking force upon a rotatable disc require the continued supply ofpressurized fluid to actuate the service brake. Furthermore, once theparking brake is engaged, a loss of hydraulic power releases the parkingbrake, creating an unsafe situation. Thus, if a malfunction should occurwhich would terminate operation of the fluid pumps, such as a loss inelectric power supplied to the electrically powered vehicle, the brakebecomes inoperative.

In many cases, when it is required to move an inoperable vehicle havingthe parking brake engaged, the entire brake assembly must be dismantledto release the parking brake so that the vehicle may be towed. Inaddition, considerable care must be exercised to prevent explosion ofthe compressed brake spring. To return the vehicle to service, the brakemust be reassembled. Such a procedure is time consuming and, in mostcases, produces a variance in the braking force by disturbing thecoordination and precision orginally established between interactingcomponents of the brake assembly. If this hazard is to be avoided, theonly alternative is replacing the inoperative brake assembly with anoperative brake assembly. In most instances, installing a complete brakeassembly on a vehicle in a working environment requires considerableeffort resulting in loss of vehicle efficiency.

There is need for a brake mechanism operable in a hydraulic circuit thatwill remain operational in the event of loss of hydraulic power to thesystem and can be efficiently serviced without requiring extensiverepair of the brake mechanism and alteration of the braking force.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a brakemechanism that includes a housing having a slot for receiving arotatable disc and an open end portion. A chamber is provided in saidhousing for receiving pressurized fluid from a source. A plurality ofbraking pads are positioned in the slot oppositely of the disc. A firstbraking assembly is reciprocally positioned in the housing for axialmovement toward and away from the disc. The first braking assembly isoperable to move the braking pads into braking engagement with the disc.A second braking assembly is reciprocally positioned in the fluidchamber and applies a brake actuating force to the first brakingassembly to move the braking pads into braking engagement with the discin response to the fluid pressure in the chamber. A resilient device isreleasably positioned within the housing to seal the open end portionthereof. The resilient device applies a preselected constant force uponthe second braking assembly to axially displace the second brakingassembly and exert a brake actuating force upon the first brakingassembly when the fluid pressure in the chamber is less than the forceexerted by the resilient device on the second braking assembly. Theresilient device includes apparatus for maintaining the resilient devicein a compressed state when removed from the housing open end portion.

The resilient device includes a spring assembly that is positioned inabutting relation with the second braking assembly that includes apiston having a rod portion. The spring assembly exerts a preselectedspring force on the piston to axially move the piston within the chamberwhen the fluid pressure therein is less than the spring force. Axialmovement of the piston extends the rod portion through an opening in thehousing of the brake mechanism. The end portion of the piston rod abutsthe upper end portion of an actuator lever that is pivotally mounted onthe brake assembly housing. A lower end portion of the lever contactsthe first braking assembly. Pivotal movement of the lever by movement ofthe piston rod displaces the first braking assembly to move the brakingpads into frictional and braking engagement with the rotating disc.

The brake mechanism functions as a service brake to apply a preselectedbraking force upon the rotatable disc by discharging a preselectedvolume of fluid from the chamber to reduce the fluid pressure therein.

In the event of hydraulic failure and subsequent loss of fluid pressurein the chamber, the brake mechanism remains operational. With an absenceof fluid pressure in the chamber to resist axial movement of the springassembly, the spring assembly automatically exerts upon the piston aparking brake force, which is transmitted to the first braking assembly,which is axially displaced to move the braking pads in brakingengagement with the disc to bring the vehicle to a stop. With thisarrangement, the brake mechanism functions as an automatic parking brakeand does not require the supply of fluid to the chamber to engage thebrake.

The spring assembly includes a pair of annular members coaxiallypositioned in spaced relation on a threaded rod adjacent the secondbraking assembly. The first annular member is positioned in abuttingrelation with the piston of the second braking assembly and is securedto the threaded end portion of the rod. The second annular member isreleasably secured to the brake mechanism housing and seals the open endportion thereof. A suitable spring member, such as a coil spring, a discspring or the like, having a preselected spring constant, axiallysurrounds the annular members and is retained between the end portionsthereof. With the second annular member immovably secured to the brakeassembly housing, the spring member exerts a preselected force upon thefirst annular member to move with the rod and exert a force upon thesecond braking mechanism. By axially advancing the rod away from thesecond braking mechanism, the first annular member is advanced towardthe second annular member to compress the spring member therebetween.The annular members are locked in position on the rod to maintain thespring member in a compressed state to permit safe removal of the entirespring assembly from the housing. In this manner, the spring assemblymay be efficiently serviced or replaced with another spring assemblyhaving a different spring constant.

Accordingly, the principal object of the present invention is to providea brake mechanism which functions as a service brake to exert apreselected braking force upon a rotatable disc by a preselected springforce acting against fluid pressure in a chamber.

Another object of the present invention is to provide a brake mechanismin which loss of pressurized fluid to the fluid chamber automaticallyactuates a park brake to retain the braking pads in frictionalengagement with the disc to prevent movement of the vehicle.

An additional object of the present invention is to provide a brakemechanism having a removable spring assembly for actuating the brakemechanism in which the spring member may be locked in a compressed statewhen spring assembly is removed from the housing to prevent an explosionof the spring and the other components and then provide for efficientreplacement or servicing of the spring assembly.

These and other objects of this invention will be more completelydisclosed in the following specification, the accompanying drawings andthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the brake mechanism illustrating a spacerbracket that is secured between the inner and outer brake housings formounting the brake assembly on a vehicle frame adjacent the rotatabledisc.

FIG. 2 is a sectional view, in side elevation, taken along the line 2--2of FIG. 1, illustrating the braking pads positioned in brakingengagement with the rotatable disc.

FIG. 3 is an end view of the brake mechanism, taken along the line 3--3of FIG. 1, illustrating, in phantom, the braking pads that are securedto the outer half of the brake housing.

FIG. 4 is a sectional view in side elevation of another embodiment ofthe brake mechanism.

FIG. 5 is an end view of the brake mechanism, illustrated in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, there is illustrated a brake mechanismgenerally designated by the numeral 10 that is incorporated in ahydraulic circuit and functions to apply a braking force upon arotatable disc 12. The disc 12, for example, may be mounted on a brakeshaft of a vehicle drive train or drivingly connected to the vehiclewheels. In a specific embodiment, the brake mechanism 10 may beoperatively associated with a conventional gear reduction system of amine haulage vehicle, such as a shuttle car, in which the mechanism 10is accessibly mounted on the vehicle for making repairs and adjustments.

Referring to FIGS. 1 and 3, there is illustrated the brake mechanism 10that includes a brake housing generally designated by the numeral 14that has a first housing member 16 separated from a second housingmember 18 by a spacer bracket 20. The spacer bracket 20 is secured tothe housing members 16 and 18 by bolts 21 that extend through alignedbores of the bracket 20 and housing members 16 and 18. The spacer 20 isprovided with outwardly extending arm portions 23 and 25 having bores 27and 29 through which fastening devices may be extended to secure thebracket 20 to the sidewall of the vehicle for mounting the brakemechanism 10 adjacent the rotatable disc to be braked. With the brakehousing 14 secured to the vehicle frame by the spacer bracket 20, thebrake mechanism 10 is easily disassembled by removing the bolts 21 fromthe housing member 16 to free the member 16 from connection with thespacer bracket 20. With this arrangement, the components of the brakemechanism are conveniently accessible for repair or replacement, as willbe further hereinafter discussed.

The first and second annular members 16 and 18 together with the spacer20 form an annular chamber 31 having an opening 33 which extends throughthe housing member 16. A reciprocating brake actuator generallydesignated by the numeral 24 is sealingly positioned for axial movementin the chamber 31 and divides chamber 31 into a first chamber 22rearwardly of actuator 24 for receiving pressurized fluid from a sourceand a second chamber 35 sealed from chamber 22 forwardly of the actuator24. The actuator 24 reciprocates within the chamber 35. The fluidchamber 22 is connected to a hydraulic line through a fluid connection(not shown). Pressurized fluid is conducted to a chamber 22 to resistand balance the constant braking force generated by the brake actuator24. When the fluid pressure in the chamber 22 is less than the brakingforce of the brake actuator 24, a resultant braking force is transmittedto a brake applicator generally designated by the numeral 26. A lever 28that is pivotally mounted on an ear 30 extending outwardly from thesecond housing member 18 transmits the brake actuating force of theactuator 24 to the applicator 26.

It should be understood that the sole function of the lever 28 is totransmit the brake actuating force of the brake actuator 24 to the brakeapplicator 26. The arrangement may be so modified that the brakeactuator 24 is coaxially mounted with the brake applicator 26 forimparting a braking force upon the disc 12, as later described for theembodiment illustrated in FIGS. 4 and 5. The arrangement illustrated inFIGS. 1-3 is preferred where limitations in mounting space do not permitcoaxially mounting of the brake actuator 24 with the brake applicator26. Thus, the brake mechanism 10 is actuated by venting pressurizedfluid from the chamber 22 and the mechanism is released by conductingpressurized fluid into the chamber 22.

The brake applicator 26 is slidably and sealingly disposed within a cupshaped recess 32 formed in the lower portion of the housing member 18. Aslot 34 is formed by the lower portions of the housing members 16 and 18adjacent to the recess 32 and receives the rotatable disc 12. Brakingpads or linings 36 and 38 are nonrotatably secured to the end portion ofthe brake applicator 26 and the housing first annular member 16 withinthe slot 34. The brake actuating force transmitted by the lever 28 movesthe applicator 26 axially in the recess 32 to thereby urge the brakingpads 36 into braking engagement with the friction surface 40 of the disc12. The braking pads 38 are secured to the housing member 16 and offerno frictional resistance to rotation of the disc 12 when the brake isreleased. Upon engagement of the pads 36 with the disc 12, the pads 38frictionally engage the disc friction surface 42. In this manner, thebraking pads 36 and 38 exert a braking force upon the disc 12 toovercome the torque of the rotating disc 12 to slow or stop the vehicle,as desired.

In greater detail, the brake applicator 26 includes an annular brakeapplicator piston 44 having a piston rod 46 integral therewith. Thepiston rod 46 extends through bore 48 in the lower portion of thehousing second annular member 18. A guide plunger 50 is sealinglysecured in the bore 48 by O-rings 52. Bore 54 of guide plunger 50receives the piston rod 46 for axial movement relative to the guideplunger 50. Seals 56 and O-rings 58 prevent dirt from entering therecess 32 and maintain substantially frictionless movement of the pistonrod 46 in the guide plunger bore 54.

The annular brake applicator piston 44 moves axially within the recess32 toward and away from the disc 12. An annular abutment member 60 isaxially and nonrotatably secured to the end portion of the piston 44 bya threaded member 62. Braking pads 36 are nonrotatably secured to theend portion of the abutment member 60 adjacent to the friction surface40 of the disc 12. The braking pads 36 are thus arranged to move axiallywith the abutment member 60 in the slot 34 relative to the disc 12. Thebraking pads 38 are suitably secured to the lower end portion of thehousing first annular member 16 and are axially aligned with the brakingpads 36 opposite the disc friction surface 42.

A cup-shaped sleeve member 64 is slidably positioned in the recess 32and is axially mounted on the annular brake applicator piston 44. Theend portion of the sleeve member 64 abuts shoulder 66 of annular piston44 to form an annulus 68 between the piston 44 and the sleeve member 64.A coil spring 70 is positioned within the annulus 68 and abuts shoulder72 of the sleeve member 64 and the annular piston shoulder 66. The coilspring urges the annular piston 44 away from the disc 12 to therebyrelease the braking pads 36 and 38 from braking engagement with thefriction surfaces 40 and 42 when the fluid pressure in the chamber 22exceeds the brake actuating force of the brake actuator 24. O-rings 74and 76 seal the annular piston 44 and sleeve member 64 relative to therecess 32.

As stated hereinabove, the brake actuating force is transmitted to thebrake applicator 26 by the lever 28. The lever 28 is pivotally securedto the ear 30 by a lever pin 78. The lever 28 includes a lower endportion 80 having a bearing surface 82 and an upper end portion 84having a threaded bore 86 for receiving adjusting screw 88. With thisarrangement, axial movement of the brake actuator 24 is transmitted bythe lever 28 as it pivots about the lever pin 78 to urge the bearingsurface 82 of the lever end portion 80 into abutting relation with theend of piston rod 46. Consequently, the force acting upon the piston 44overcomes the resistance offered by the coil spring 70 to move thebraking pads 36 and 38 into braking engagement with the disc 12.

The brake actuator 24 is operable to transmit a preselected brakingforce through the lever 28 to the brake applicator 26 and the brakingpads 36 and 38. The brake actuator 24 includes an annular actuatingpiston 90 that is slidably and sealingly disposed within the annularchamber 22. A piston rod 92 of the piston 90 extends through a bore 94in the housing member 18. A guide plunger 96 is positioned within thebore 94 and includes a bore 98 for reciprocally receiving the piston rod92. With this arrangement, the guide plunger 96 maintains axialalignment of the piston rod 92 as it reciprocates within the chamber 22and bore 94. O-rings 100 and 102 maintain a seal for the guide plunger96 relative to the housing member 18 and the piston rod 92.

An O-ring seal 104 surrounds the annular piston 90 and a felt seal 106is bonded to piston shoulder 108 to provide a fluid tight seal betweenthe fluid chamber 22 and the chamber 35 forward of the piston 90. Aself-contained spring assembly generally designated by the numeral 110is positioned within the annular chamber 35 forward of the piston 90 andfunctions to exert upon the piston 90 a preselected brake actuatingforce. When the fluid pressure in the chamber 22 is less than the springforce of the spring assembly 110, a braking force is applied to the disc12.

The spring assembly 110 includes a plunger 112 slidably positioned inabutting relation with the annular piston 90 in chamber 22. Plunger 112includes a flanged end portion 114 that engages in abutting relation theshoulder 108 of the piston 90 to thereby assure axial movement of thepiston 90. The plunger 112 has a longitudinal bore 116 that is axiallyaligned with the piston rod 92. A rod member 118 having a an enlargedhead 120 and a threaded end portion 122 is threadedly engaged to theplunger 112 within the threaded bore 116. In addition, weld 124 securesthe rod end portion 122 to the plunger 112 so that axial movement of therod 118 within the chamber 35 is transmitted to the plunger 112.

A second annular plunger 126 having a cup-shaped configuration ismounted on the rod member 118. The plunger 126 has an axial bore 128that is aligned with the bore 116 of plunger 112. The bore 128 connectswith a threaded bore 130 of increased diameter. The plunger 126 includesa flanged end portion 132 that serves to seal the open end portion 33 ofthe chamber 35. The flanged end portion 132 abuts the wall of thechamber 35. An annular shoulder 129 on housing 16 overlies the flangedend portion 132 of plunger 126. The plunger 126 is nonrotatably securedrelative to the housing member 16 by a pin 131. With this arrangement,the plunger 126 is axially immovable and non-rotatable within thechamber 35.

The threaded bore 130 of the plunger 126 receives for axial movementrelative thereto an adjusting sleeve generally designated by the numeral134. The adjusting sleeve 134 has an outer threaded body portion 136that is threadedly secured in the bore 130 of plunger 126. The adjustingsleeve 134 has a bore 138 extending through the body portion 136 inwhich the rod member 118 is positioned for axial movement. The adjustingsleeve 134 includes a cap 140 having an inner serrated surface 142 thatis arranged to move in and out of engagement with the outer surface ofthe plunger flanged end portion 132. With this arrangement, when theadjusting sleeve 134 is advanced into the threaded bore 130 of theplunger 126, as illustrated in FIG. 2, further advancement of theadjusting sleeve 134 is prevented when the serrated edge 142 engages theflanged end portion 132.

A pair of concentrically positioned coil springs 144 and 146 having apreselected spring constant surround the plungers 112 and 126 and abutthe respective flanged end portions 114 and 132. The abutment providedfor the plunger 126 by the shoulder 129 of housing member 16 immovablysecures the plunger 126 relative to the rod member 118. Accordingly, thesprings 144 and 146 act upon the plunger flanged end portion 114 to urgethe plunger 112 into contact with the piston 90. Thus, the piston 90 ismoved axially toward the lever 28. The piston rod 92 moves through thebore 98 of the guide plunger 96 and into contact with the end portion ofthe lever adjusting screw 88. The lever 28 then pivots about the pin 78to transmit the brake actuating force through the piston rod 46 and tothe brake applicator piston 44 and thereby move the braking pads 36secured to the end of the piston 44 into braking engagement with thefriction surface 40 of the disc 12. With the above describedarrangement, a resultant balancing force is exerted upon the actuatingpiston 90 to retain the piston 90 immovable within the chamber 22 whenthe fluid pressure in the chamber 22 exceeds or is equal to the springforce exerted by the coil springs 144 and 146 upon the piston 90.

To release the braking force upon the pads 36 and 38, fluid is conductedinto the chamber 22 until the fluid pressure exceeds the force of thesprings 144 and 146. The piston 90 and the piston rod 92 move axially ina direction away from the adjusting screw 88 such that the actuatingforce is removed from the lever 28 and consequently, the braking pads 36and 38 move out of braking engagement with the disc 12. Accordingly, byventing the chamber 22, the braking action is once again initiated whenthe spring force exceeds the fluid pressure in chamber 22. In thisfashion, the brake assembly 10 operates as a service brake in which thevolume of fluid in the chamber 22 controls the magnitude of the brakingforce exerted upon the disc 12.

In the event of failure in the hydraulic circuit of the brake, as forexample a loss of electric power to the pump which supplies thepressurized fluid to the chamber 22, the brake assembly 10 remainsoperational. Without fluid in chamber 22 to resist the force of thesprings 144 and 146, the braking force transmitted through the lever 28to the actuator piston rod 46 maintains the braking pads 36 and 38 inbraking engagement with the disc 12. With this arrangement, an auxiliaryor parking brake is automatically actuated to generate a resistive forceupon the actuating piston 90.

A spring assembly having a preselected spring force may be inserted inthe housing 14 to meet any given torque requirement. The versatilityprovided by the self-contained spring assembly 110 eliminates thenecessity of installing an entire brake assembly on the vehicle to meeta change in the torque of the brake shaft. Thus, by merely exchangingspring assemblies in the brake housing 14, a variable braking force maybe provided for the brake mechanism 10.

Continued application of the braking pads 36 and 38 into brakingengagement with the disc 12 produces wear of the pads. Accordingly, asthe thickness of the braking pads 36 and 38 decreases, increaseddisplacement of the actuating piston 90 is required to maintain thebraking pads in braking engagement with the disc 12. As the thickness ofthe braking pads decreases, the actuating piston 90 moves to a positioncloser to the rear wall of the actuating chamber 22. In addition, therod member 118 secured to the plunger 112 moves axially in the bores 128and 138 under the force of the coil springs 144 and 146. The relativeposition of the rod member 118 in the adjusting sleeve 134 provides avisual indication of the wear condition of the braking pads 36 and 38.Therefore, by providing a plurality of reference points 148 on theinside surface of the body portion 136, the amount of wear of thebraking pads 36 and 38 is indicated by the alignment of the end of thecap 120 with a particular reference point. Eventually, the cap 120 willreach a position within the adjusting sleeve 134 indicating that thereis need to install new braking pads.

Further in accordance with the present invention, provision is made toefficiently remove the spring assembly 110 from the brake housing 14.Replacement of the spring assembly 110 is necessitated when it isdesired to vary the spring force of the brake actuator 24 or when it isdesired to release the parking brake when the fluid chamber 22 has beenvented so that the vehicle may be moved. Replacement of the springassembly 110 is accomplished by threadedly retracting the adjustingsleeve 134 out of the plunger 126. When the adjusting sleeve 134 hasbeen retracted to a position where the shoulder 150 of the sleeve abutsthe cap 120, continued rotation of the adjusting sleeve 134 in the samedirection moves the rod member 118 and the plunger 112 axially in thechamber 22 to compress the springs 144 and 146. Axial movement of theplunger 112 will continue away from the forward face of the piston 90until the adjacent faces of the plunger 112 and 126 are in abuttingrelation. With this arrangement, the adjusting sleeve 134 is threadedlyengaged to the plunger 126 and is, therefore, axially immovable relativethereto. Thus, with the shoulder 150 and the cap 120 positioned inabutting relation, the rod member 118 is axially immovable relative tothe plunger 126 and the springs are locked in a compressed state toprevent their explosion when removed from the housing 14.

With the coil springs 144 and 146 locked in a compressed state, thehousing member 16 is released from connection with the spacer bracket 20by removing the bolts 21. With the housing member 16 removed from thebrake mechanism 10, the spring assembly 110 is then freely removablefrom the chamber 35. In this manner, the spring assembly 110 may beefficiently serviced or replaced without need to separately remove thesprings 144 and 146 from the other components of the brake mechanism.After servicing, when the spring assembly 110 is inserted back into thechamber 35 and the housing 16 bolted to the bracket 20, the springs 144and 146 are fully operable to exert the same actuating force upon thepiston 90.

Referring to FIGS. 4 and 5, there is illustrated another embodiment ofthe brake mechanism 10 that is hydraulically controlled to apply abraking force upon the rotatable disc 12. As stated hereinabove, thedisc 12 may be operatively connected to a vehicle wheel or mounted on abrake shaft of a vehicle drive train. However, in any case, the brakeassembly 10 is mounted to permit accessibility for making repairs andadjustments. The brake assembly 10 illustrated in FIG. 4 includes anouter housing 152 that is connected by nut and bolt assemblies 154 and156 to a housing cylinder 158. The outer housing 152 and housingcylinder 158 form a slot 160 for receiving the rotatable disc 12.Braking pads or brake linings 162 are nonrotatably secured to the lowerend portion of housing 152 by threaded members 164. Positionedoppositely of the braking pads 162 within the slot 160 are braking pads166 that are secured by threaded members 168 to a brake applicator 170.The brake applicator 170 is slidably retained within an cylindricalrecess 172 of the housing cylinder 158. The application of a brakeactuating force to the brake applicator 170 moves the applicator axiallywithin the recess 172 to thereby urge the braking pads 166 and 162 intobraking engagement with the friction surfaces 174 and 176 of the disc12. The braking pads 162 and 166 are axially aligned opposite oneanother and do not frictionally engage the disc 12 when the brake isreleased.

The cylindrical recess 172 of the housing cylinder 158 is connected by acylindrical passageway 178 to an annular fluid chamber 180. A brakeactuator generally designated by the numeral 182 is axially movablewithin the chamber 180 and seals the open end portion thereof. A sealmember 184 surrounds the brake actuator 182 and abuts the inner wall ofthe housing cylinder 158 to provide a fluid-tight seal around theactuator 182. As above discussed for the fluid chamber 22 of the brakeassembly 10 illustrated in FIG. 2, the fluid chamber 180 in FIG. 4 isconnected to a hydraulic line through a conventional fluid connection(not shown) to receive pressurized fluid from a source.

The brake actuator 182 includes an annular piston 186 that is slidablypositioned within the fluid chamber 180 and includes a tubular portion188 having an axial bore 190. The tubular portion extends through thepassageway 178 in the housing 158 and includes an end portion 192 thatis positioned in substantially abutting relationship with the brakeapplicator 170. Seal members 191 and 193 surround end portion 192 in thepassageway 178.

The brake applicator 170 includes an enlarged end portion 194 thatsupports the braking pads 166, as hereinbefore described, and a tubularbody portion 196 that extends rearwardly therefrom through the tubularmember 188 of the piston 186. The end portion 194 and the body portion196 of the brake applicator 170 are axially movable within the housingof cylinder 158 and nonrotatably retained therein by a pin 198 thatextends through a longitudinal slot 200 of housing cylinder 158 into theend portion 194. The tubular body portion 196 includes an axial bore 202and a longitudinal slot 204 that extends substantially the length of thebody portion 196.

A chamber 206 extends forwardly of the brake actuator 182 in the housingcylinder 158 and has an open end portion 208 and a threaded portion 209.A spring assembly generally designated by the numeral 210 is positionedwithin the chamber 206 and seals the open end portion 208 of the housing158. The spring assembly 210 exerts a preselected force upon the brakeactuator 182. When the brake assembly 10 is maintained in a deactivatedcondition, the fluid pressure in the chamber 180 exerts a force upon thepiston 186 sufficient to resist and balance the constant braking forceexerted on the opposite face of the piston by the spring assembly 210.In this manner, the brake actuator 182 remains stationary within thechamber 180 so that the brake applicator 170 maintains the braking pads166 removed from frictional engagement with the disc 12.

When the vehicle is to be slowed or brought to a complete stop, apreselected volume of fluid is discharged from the chamber 180 such thatthe fluid pressure in the chamber 180 is less than the actuating forceexerted by the spring assembly 210 upon the piston 186. Accordingly, thepiston 186 is displaced axially within the chamber 180 toward the disc12 to thereby urge the tubular end portion 192 into abutting relationwith the brake actuator 170. This moves the actuator 170 to, in turn,urge the braking pads 162 and 166 into frictional engagement with thedisc 12.

The magnitude of the braking force applied to the disc 12 is determinedby the volume of fluid vented from the chamber 180. Should a malfunctionoccur in the hydraulic system that supplies the pressurized fluid to thechamber 180, the brake assembly 10 remains operational. Thus, aninterruption in the flow of fluid to the chamber 180 decreasing thefluid pressure in the chamber to less than the spring force of theassembly 210 axially displaces the piston 186 to move the applicator 170toward the disc 12 so that the braking pads 162 and 166 engage the disc12 to slow or stop the vehicle. Thus, with this arrangement, anauxiliary or parking brake is automatically actuated in the event thefluid pressure within the chamber 180 diminishes.

The spring assembly 210 includes a plunger 212 that is axially alignedwith the brake actuator 182 and the brake applicator 170. The plunger212 includes an axial bore 214 and an annular end portion 216 that ispositioned in abutting relationship with the piston 186. A threaded bolt218 having a nut 220 secured to one end portion thereof extends throughthe axial bore 214 of the plunger 212 for slidable axial movementrelative thereto. The bolt 218 has at the opposite end portion a cap 222that is secured to the bolt 218 by a pin 224. The end portion of thebolt 218 is positioned within the axial bore 202 of the brake applicator170 with the pin 224 axially movable within the slot 204 so that thebrake applicator 170 can move relative to the bolt 218.

A retractor 226 having a cup-shaped configuration has an axial threadedbore 228 threadedly secured to the bolt 218. The retractor 226 has alongitudinal body portion and a hexagonal end portion 230. An annularend cap 232 having an annular recess 234 and a bore 236 is engaged tothe threaded portion 209 of the housing cylinder 158 to thus seal theopen end portion of the cylinder 158. The retractor 226 extends throughthe bore 236 with the end portion 230 thereof positioned in abuttingrelationship with an outer shoulder 238 of the end cap 232.

A lock bar 240 is secured by a bolt 242 to the end cap 232 asillustrated in FIGS. 4 and 5. The lock bar 240 has an end portion 244that is positioned in overlying abutting relationship with the hexagonalend portion 230 of the retractor 226. With this arrangement, theretractor 226 is axially fixed within the housing cylinder 158 on thebolt 218 by the abutting relationship of the shoulder 238 and the lockbar end portion 244 with the end portion 230. The housing cylinder 158has a transverse slot 246 that overlies a transverse bore within the endcap 232 for receiving a set screw 248. The set screw 248 is advancedthrough the transverse bore 246 and the end cap 232 into engagement withthe bolt 242. In this manner, the end cap 232 is nonrotatably secured tothe housing cylinder 158.

A resilient member such as a Belleville spring or a disc spring 250having a preselected spring constant is positioned in surroundingrelationship with the plunger 212 having the end portions of the spring250 positioned in abutting relationship at one end with the end cap 232and at the other end with the piston 186 and the annular end portion 216of the plunger 212. With the end cap 232 axially immovable within thehousing cylinder 158, the disc spring 250 exerts an axial force upon theplunger 212 and the piston 186. Accordingly, the spring force istransmitted through the piston 186 to the brake applicator 170 tothereby axially displace the brake applicator 170 and urge the brakingpads 162 and 166 into frictional engagement with the rotating disc 12.

The spring assembly 210 may be removed from the housing cylinder 158 inmuch the same manner as hereinabove described for the spring package110, illustrated in FIG. 2. The spring assembly 210 may be removed inorder to replace the spring 250 for a spring of a different forceconstant or in order to release the parking brake when the fluid chamber180 has been completely vented to permit moving the vehicle. To removethe spring assembly 210 from the housing cylinder 158, the lock bar 240is removed from abutting relation with retractor end portion 230. Thenthe retractor is rotated in a clockwise direction retracts the bolt 218in the axial bore 202 of the tubular body portion 196 of brakeapplicator 170. The pin 224 in the slot 204 prevents rotation of thebolt 218 until the cap 222 contacts the shoulder 252 of plunger 212.Then, further rotation of the retractor 226 retracts the bolt 218 andnut 220 to the position illustrated, in phantom, in FIG. 4. The cap 222of bolt 218 in this position abuts the shoulder 252 of plunger 212. Inthis manner, the bolt 218 retracts the plunger 212 away from the disc 12to compress the disc spring 250 between the plunger end portion 216 andthe base of the end cap 232. With the spring in a fully compressedstate, the forward end portion of the plunger 212 abuts the base of theend cap 232 and the cap 222 of the bolt 218 abuts the plunger shoulder252. The spring assembly 210 is now locked in a compressed staterestrained from exploding and prepared for convenient and efficientremoval as a unit from the housing cylinder 158.

Removal of the spring assembly 210 is accomplished by first removing theset screw 248 from the slot 246 and the bore in the end cap 232. Inaddition, the bolts 254 that secure the end cap 232 to the housingcylinder 158, as illustrated in FIG. 5, are removed. Then, by applyingan additional torque to the retractor 226, the end cap 232 together withthe remaining components of the spring assembly 210 are axiallyretracted out of the chamber 206 of the housing cylinder 158. Thus, thespring assembly 250 is conveniently and safely removed from the housingcylinder 158 for repair or replacement. To restore the brake mechanism10 to service, the spring assembly 250 is positioned in the housingcylinder 158 and the end cap 232 bolted in place. Then the retractor 226is rotated in a counterclockwise direction until nut 220 abuts theshoulder of the retractor as illustrated in FIG. 4. The lock bar 240 isreplaced so that the end portion 244 contacts the retractor end portion230.

According to the provisions of the patent statutes, we have explainedthe principle, preferred construction and mode of operation of ourinvention and have illustrated and described what we now consider torepresent its best embodiments. However, it should be understood that,within the scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

We claim:
 1. An improved brake mechanism comprising,a brake housing,said brake housing including a first housing member and a second housingmember, said first and second housing members being positioned in spacedrelation, a spacer member positioned between and in abutting relationwith said first and second housing members, bolt means extending throughsaid first housing member, said spacer member, and said second housingmember for releasably connecting said first and second housing membersand said spacer member, a chamber formed by said first and secondhousing members and said spacer member, said chamber having a first openend portion and a second open end portion, a brake actuator movablypositioned within said chamber and having an end portion extendingthrough said second open end portion of said chamber, a lever memberpivotally connected to said second housing member and having one endportion adjacent said brake actuator end portion, a cup-shaped recessformed in said second housing member and positioned below said chamber,an opening extending through said second housing member into saidcup-shaped recess, a slot in said brake housing formed by said first andsecond housing member and said spacer member, said slot being positionedadjacent to said recess and adapted to receive a rotor member, a brakeapplicator slidably positioned within said recess, said brake applicatorhaving an end portion extending out of said recess and through saidopening of said second housing member to a position adjacent said leverother end portion, said brake actuator being operable to pivot saidlever and move said brake applicator into braking engagement with therotor member, means to urge said brake applicator into a brakedisengaged position, seal means surrounding said end portion of saidbrake actuator for sealing said second open end portion of said chamber,said chamber being adapted to receive pressurized fluid from a source toovercome a force applied by said brake actuator, a first annular memberpositioned in said chamber in abutting relation with said brakeactuator, an axial bore in said first annular member, a second annularmember positioned in said chamber and closing said first open endportion of said chamber, an axial bore in said second annular member, arod member extending through said axial bores of said first and secondannular members, said rod member having a portion positioned within saidaxial bore of said first annular member and a portion positioned withinsaid axial bore of said second annular member, said rod member having anenlarged first end portion positioned for movement in said axial bore ofsaid second annular member, a retractor member positioned in said boreof said second annular member, a bore extending through said retractormember, said rod member extending through said bore of said retractormember, resilient means positioned between said first and second annularmembers and having opposite end portions positioned in abutting relationwith said first and second annular members respectively, said resilientmeans being operable to exert a preselected spring force through saidfirst annular member upon said brake actuator and axially move saidbrake actuator to apply a force upon said brake applicator when thefluid pressure in said chamber is less than the force exerted by saidresilient means on said brake actuator, and said retractor member beingoperable upon rotation to move said first and second annular members inabutting relation and compress said resilient means between said firstand second annular members to permit removal of said first and secondannular members, said resilient means, said rod member, and saidretractor member as a single unit from said chamber first open endportion.
 2. An improved brake mechanism as set forth in claim 1 whichincludes,said brake actuator having a shoulder portion positionedoppositely of said first annular member, said first annular memberhaving a cylindrical body portion with a flanged end portion, saidflanged end portion being movable into and out of abutting relation withsaid brake actuator shoulder, said second annular member having acylindrical body portion with a flanged end portion, said first annularmember cylindrical body portion positioned adjacent to said secondannular member cylindrical body portion, said first housing memberhaving an inturned flanged end portion at said chamber first open endportion, said second annular member flanged end portion abutting saidfirst housing member inturned flanged end portion, said resilient meanspositioned in surrounding relation with said cylindrical body portionsof said first and second annular member, and said resilient means havingopposite end portions positioned in abutting relation with said flangedend portions of said first and second annular members so that saidresilient means acts upon said first annular member flanged end portionto move said brake actuator toward said one end portion of said lever.3. An improved brake mechanism as set forth in claim 1 whichincludes,said rod member having a second end portion secured to saidfirst annular member within said axial bore thereof, said retractormember having a body portion threadedly engaged to said second annularmember within said axial bore thereof, said retractor body portion andsaid bore forming a shoulder portion, said shoulder portion beingmovable into abutting relation with said rod member enlarged first endportion upon rotation of said retractor member out of said first housingmember, and said retractor member being operable upon continued rotationto further move said rod member enlarged first end portion and move saidfirst annular member away from said brake actuator to fully compresssaid resilient means between said first and second annular members. 4.An improved brake mechanism as set forth in claim 1 which includes,saidretractor member arranged to move into abutting relation with said rodmember enlarged first end portion and restrain said rod member frommoving axially relative to said retractor member to lock said resilientmeans in a compressed state and permit removal of said resilient meansfrom said chamber of said brake housing.
 5. An improved brake mechanismas set forth in claim 1 wherein,said spacer member includes outwardlyextending arm portions, and said arm portions having bores adapted toreceive fastening means for releasably mounting said first and secondhousing members relative to the rotor member.